N IsoCamp - Ehleringer
Transcript of N IsoCamp - Ehleringer
Biogeochemistryoftheoceans
HowardJ.Spero
UniversityofCaliforniaDavis
N
S
s t a b l e i s o t o p e s . u t a h . e d u
IsoCampSIRFER @ Utah
2017
6/26/17
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Talk Outline• The ocean-atmosphere-hydrologic cycle system
and oxygen isotope geochemistry • Dissolved inorganic carbon in the ocean - the
CO2 buffering system • A geochemists view of ocean circulation - the
oceanic conveyor belt • O & C isotope geochemistry of carbonates-
linking the present with the past • The 21st Century Frontier: Emerging
Technologies at the stable isotope:element interface; lasers, SIMS and NanoSIMS
The ocean – precipitation linkage
http://web.sahra.arizona.edu/programs/isotopes/oxygen.html
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Rainout and Rayleigh Distillation
Ocean
Excessive Rayleigh Fractionation is observed on glacial ice sheets
http://earthobservatory.nasa.gov/Features/Paleoclimatology_OxygenBalance/
e.g. SLAP (Standard Light Antarctic Precipitate); δ18O=-55.5‰, δD=-427.5‰
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Rainout and Rayleigh Distillation
Antarctica
The oxygen and hydrogen isotope composition of ice reflects the mean air temperature over the glacier during
snowfall
As temp drops, δ18O of water decreases with a
slope of 0.7‰/oC
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Impact of Rayleigh Fractionation on glacial oceans – 20 ka
https://upload.wikimedia.org/wikipedia/commons/6/6f/Glacial_effect_hg.png
So 100m sealevel change ~1‰ increase (decrease) in δ18Osw
100 m Avg ocean depth is 3800 m
Avg ice sheet ~-35 to -40‰
δ18O = 0‰
δ18O = -10‰
δ18O = -3‰ δ18O = -20‰
δ18O = -40‰
Cooke and Rohling, 2001
Modern Hydrologic Cycle and Isotope Geochemistry
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http://d32ogoqmya1dw8.cloudfront.net/images/eslabs/hurricanes/3d_hadley_md.v3.jpg
Global Atmospheric Circulation Patterns
ITCZ
Hadley
cell
Ferrel cell
Polar cell
Global Atmospheric Circulation Patterns
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Wind-Driven Surface Current Patterns Reflect Overlying Atmospheric Circulation Patterns
http://www.goes-r.gov/users/comet/tropical/textbook_2nd_edition/navmenu.php_tab_4_page_3.1.0.htm
Gyres
Evaporation:Precipitation Patterns Define Surface Salinity Variations in the Ocean
Sub-tropical hi Pressure; E>P yields hi
Salinity
Equatorial and Hi latitudes; E<P yields low
salinity
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Surface Salinity Patterns - Highest Salinity is Found in the Central Gyres Under the Subtropical Hi P Zones
http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NODC/.WOA98
δ18Owater can be Used as a Salinity proxy Important: Global Salinity vs δ18Osw equations are NOT VALID
http://data.giss.nasa.gov/o18data/
High salinity – high δ18Osw in central gyres
Low salinity – low δ18Osw in high lats and equatorial regions
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Regional Salinity:δ18Ow Relationships have Different Freshwater Endmembers
Y-intercepts reflect average freshwater input to each region
Fairbanks & Charles (1992)
Note Low Salinity Regions of Ocean - Each has a Different Freshwater Endmember
http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NODC/.WOA98
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http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NODC/.WOA98
Atlantic is Saltier than the Pacific - Why?
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http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NODC/.WOA98
Atlantic is Saltier than the Pacific
What parameters control the carbon isotopic composition of
the ocean?
**Important: Graduate Survival Guide for understanding CO2 systematics, isotope equilibria and the carbon system in marine and freshwater environments: Zeebe and Wolf-Gladrow, 2001, CO2 in seawater: Equilibrium, kinetics, isotopes. Elsevier Press
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After Andy Ridgwell (2010)
Henry’s Law pCO2=CO2(aq)/KH
Chemical and Biological Processes Control Carbon Cycling in the Oceanic Buffer System
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Bjerrum Plot of Dissolved Carbon Species in Seawater Note: H2CO3* is only ~1-2% of DIC
Note: [H2CO3]* = [CO2aq] + [H2CO3]
From Zeebe 2007
Modern Range pH ~7.7 – 8.3 D
IC
Physical mechanism controlling the δ13C of ΣCO2 (=DIC) in the ocean: equilibrium fractionation at the ocean surface
From Lynch-Stieglitz et al (1995); based on data from Zhang et al (1995)
Today δ13C atmospheric CO2 is ~ -8.2‰ so δ13CΣCO2 sfc ranges from ~-0.5 to 2.5‰
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Biological Pump Controls the Vertical Carbon Isotope Gradient in the Ocean
δ13CDIC of Surface Waters Reflects a Combination Of Physical and Biological Controls
Pacific Meridional Transect along 120oW (pre 1980)
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Vertical Distribution Of δ13CDIC and PO4 In the North Pacific
PO4 and δ13CDIC covary linearly in the Ocean; δ13C can be used as a Proxy for Dissolved Nutrients
m = 1.1‰ µmol-1 kg-1
Effect is due to rather constant C:N:P relationship in marine organisms Redfield Ratio - 106:16:1
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What Causes Inter-ocean Differences in nutrients such as [PO4] and other non-conservative tracers?
Vertical O2 profile reflects density structure of ocean with Upper pycnocline
and oxygen minimum zone (OMZ)
Subtropical Pacific
Subtropical Atlantic
OMZ
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Deep-water Thermohaline Circulation is the Lower Limb of the Oceanic Conveyor Belt
NADW
NADW formation regions
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Iceland Faeroe Ridge w/Norwegian Sea and N. Atlantic
Schafer-Neth 1998
Surface flow
Surface flow
Iceland Faeroe Ridge w/Norwegian Sea and N. Atlantic
Schafer-Neth 1998
Deep flow
Deep flow
NADW
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Deep-water Thermohaline Circulation is the Lower Limb of the Oceanic Conveyor Belt
NADW
AABW
Weddell Sea AABW formation region; primarily during the
winter when salt gets excluded during sea ice formation *
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Profile of Atlantic Circulation; Vertical distribution is controlled by density
http://homepage.smc.edu/grippo_alessandro/oce1.html
Meridional Overturning Circulation is ultimately controlled by the density of surface waters in high latitude source
regions
NADW
AABW
High salinity
Low salinity
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If we remove the upper 3 km of ocean, the deep seafloor looks like this - the mid-ocean ridges
now divide the ocean basins
Broecker and Peng (1982)
The gradients link flow paths with the biological pump
O2 Concentration (µmol/kg)
Broecker and Peng (1982)
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Broecker and Peng (1982)
Nitrate Concentration (µmol/kg)
High DIC & low pH are found in the OMZ where respiration dominates
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Now, visualize the deepwater circulation in the Atlantic in Geochemical space…..
The δ13CDIC traces deep water currents and flowpaths because deep waters accumulate 13C-depleted respired CO2 during their transit through the Atlantic and around the Earth…..
Curry and Oppo 2012
NADW AABW
AAIW
0.8‰ 0.4‰
1.4‰
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NADW
δ13CDIC records the flow path and aging of thermohaline waters along the oceanic conveyor belt
AABW
δ13CDIC of surface waters – why is there a δ13CDIC low on the equator?
1978 Pacific Meridional Transect along 120oW
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The explanation lies with the impact of atmospheric wind systems on the ocean surface at the equator
Ekman Transport/Pumping: Net water movement is 90o right (N hemisphere) or left (S hemisphere) of the wind
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Ruddiman (2001)
Ekman transport - causes equatorial upwelling
Nutrient rich Low δ13CDIC
Productivity & equilibration Productivity & equilibration upwelling upwelling upwelling
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ΔpCO2 (seawater-air); Upwelling zones (red) and regions of biological productivity (blue)
Takahashi et al. (1997)
δ13CDIC Sfc Water data in Peru Current From 41oS to the Panama Canal
Pakulski et al (2007)
Eq. Upwelling zone
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http://www.geo.cornell.edu/geology/classes/Geo101/graphics/c_cycle.jpg
Carbon sequestered in the mantle, carbonate rocks and hydrocarbons cycle too slowly to influence the sub-million
year climate cycle
~45,000 GT (=1015 grams) of C are available for carbon cycling on < 106 year time
scales
Atmospheric pCO2 ‘should’ reflect balance b/n oceanic upwelling and productivity
1959-2017
Since 1959, average atmosphere CO2 concentrations have increased from 315 ppm to >412 ppm or ~30%
SIRFER #22
SIRFER #1 362 ppm
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Downloaded 6/14/2017
393 ppm
396 ppm
400 ppm
402 ppm
398 ppm
408 ppm
Natural CO2 variations reflect the seasons in the northern hemisphere
404 ppm
401 ppm
412.6 ppm
4/26/17
Rate of change - atmospheric CO2 through time
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Reconstructed atmospheric pCO2 from different proxies; The last 400 ppm world was during the Pliocene 2-5 mybp…..sealevel was likely 10-15 m higher than today
http://people.earth.yale.edu/cenozoic-evolution-carbon-dioxide
Atmospheric pCO2 1850-1990 from ice core data – what about the geochemical record?
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δ13C of atmospheric CO2 from ice cores and Mauna Loa atmospheric measurements (1850-1990)
Impact on oceanic δ13CDIC is clear; Since 1800 surface δ13C has decreased by >1.0‰
Calcareous Sclerosponge record; extension rate is ~ 200 µm/yr
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Timing of Ice Core CO2 change vs δ13C of CO2 in sclerosponge aragonite
δ13C
CO2
Atmospheric δ13C from Antarctic ice cores for the past 25 kyr – Δδ13C ~ 0.4‰
Schmitt et al 2012
Modern δ13Catm = -8.2‰
-6.3‰
-6.7‰
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Comparison of human emissions vs modern volcanic CO2 release and historical basalt flow events
Kidder and Worsley (2012)
How do we know CO2 rise is due to anthropogenic activities?
δ13C ~ -3‰ to -5‰
δ13C ~ -25‰
Modern atmosphere pCO2 δ13C = -8.2‰
Why do we care about elevated greenhouse gases such as CO2?
280 ppm
180 ppm
Interglacial CO2 maximum
Glacial CO2 minimum
2017�
83yrs x 2=166 ppm @ 2100
2100 �
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• δ18O(13C) = (18O/16Osample-18O/16Ostd) x1000 18O/16Ostd
Paleoceanography and the geochemistry of CaCO3
Foraminifera Shell Calcite (CaCO3) Marine Zooplankton
18O/16O 13C/12C
G. ruber G. menardii
16O
18O 8 protons 10 neutrons
8 protons 8 neutrons
1948, Science
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Sam Epstein et al., April 1951 Bull. Geol. Soc. Amer., Vol. 62
Harold C. Urey; Nov 5, 1948 Science, Vol. 108
Oxygen Isotopes and the Geosciences - University of Chicago circa 1950
δ18Ocalcite range for ocean
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Try to imagine being a grad student/researcher in Harold Urey’s laboratory in the early
1950’s
1955 J. Geology
Alfred Nier develops the first gas source IRMS
Harold Urey proposes oxygen
isotope thermometry
Ice age
Interglacial
Ice age
Ice age Ice
age
Foraminifera ooze from deep sea sediment; each shell is the size of a pinhead (0.5mm) Globigerinoides ruber
Lisiecki & Raymo (2005)
18O/16O controlled by Temperature, salinity, ice
volume
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Factors Affecting Calcite/Aragonite Oxygen Isotopes • δ18Owater:
a) Salinity; evaporation vs precipitationb) Latitude
freshwater systems - Rayleigh Distillation;marine systems – ice melt, coastal runoff
•Temperature
a)Equilibrium Fractionation
• pH:
a) Carbonate Ion Effect; photosyn vs resp.b) Physiology – photosynthesis (symbionts)
Factors Affecting Calcite/Aragonite Carbon Isotopes • δ13CDIC (ΣCO2):
a) Ocean Temperature (air-sea exchange)b) Community Productivity/Respirationc) Ocean Circulation – Sources/Sinks
• Physiology/Biology/Vital Effects
a) Irradiance – Symbiont photosynthesisb) Temperature – Respiration
• Ocean Chemistry:
a) pH or [CO32-] – Carbonate Ion Effect
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Culturing Foraminifera in Southern California
Los Angeles
Catalina Island
Santa Barbara
San Francisco
Santa Cruz
San Diego
Davis
Unraveling the past - Linking microfossils and their living counterparts with laboratory
experiments
CMSC/Catalina
Big Fisherman Cove – Wrigley Marine Science Center
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Orbulina universa in Culture Vessel
One of the most important climate archives - the CaCO3 shells of planktonic foraminifera
Pre-sphere, trochospiral shell form of O. universa
Spherical chamber form of O. universa
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Foraminifera are single celled protozoa that feed on zooplankton such as copepods
Spero and Parker, 1985
Orbulina universa with Artemia brine shrimp nauplius after feeding
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O. universa thickens its spherical chamber over the final 3-7 days of its lifecycle, and then
sheds its spines over a 12h period
Gametes are released within 24 hours of spine shortening, ending the life of the
individual
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Post-gametogenic O. universa from the laboratory is identical to a million year old
fossil.
Influence of symbiont photosynthesis on shell δ13C
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Spero & DeNiro (1987)
Controlled by balance between photosynthesis
and respiration
0
2
4
6
8
0 2 4 6 8
Shel
l δ13
C (‰
)
δ13C Culture Water (‰)
High Lighty = 0.92x + 1.72
Medium Lighty = 0.92x + 0.68
Low Lighty = 0.96x- 0.22
1:1 Relationship
Foraminifera geochemistry faithfully records δ13CDIC
Spero (1992)
O. universa
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Oxygen isotopic composition of Carbonates are controlled by Temperature and δ18Owater
(Bemis et al (1998); Spero et al., in prep.)
Calibration experiments across an extended temperature range enables researchers to apply O. universa δ18O data to compute
water column properties
5
10
15
20
25
30
-3-2-1012
O. universa HL (So. Cal. Bight& Puerto Rico combined)
Catalina 2000Bemis et al. (1998)Puerto Rico 1999
5
10
15
20
25
30
Tem
pera
ture
(o C)
δ18Oc - δ18O
w (‰ vs PDB)
T = 15.0 - 4.36(δshell
-δw) + 0.35(δ
shell-δ
w)2
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Bemis et al (1998)
…however, symbiont photosynthesis affects δ18O and the experimental relationship is different from inorganic precipitate studies. Can symbiosis affect shell δ18O?
Low light cultures
High light cultures
Δδ18OHL-LL = -0.35‰
The Carbonate System
ΣCO2 = [CO2] + [HCO3-] + [CO3
2-] In seawater, pH varies linearly with [CO3
2-]
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Spero et al (1997)
Serendipity…O. universa cultured under constant temperature and δ18Ow but different
[CO32-] (or pH) shows...
Spero et al (1997)
Influence of [CO32-] on O. universa δ18O
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The Mechanism - Oxygen Isotopic Fractionation Between Dissolved Carbon Species and Seawater
Bjerrum Plot of Dissolved Carbon Species in Seawater
From Zeebe 2007
Modern Range is pH ~7.7 – 8.3
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Mass Balance Calculation of δ18O of Dissolved Species Assuming Equilibrium with Seawater
Zeebe (1999)
Predicted Relationship
Experimental data fall on the predicted relationship if we can assume that during calcification, the
foraminifera use [CO32-] and [HCO3
-] In proportion to their concentration in seawater!
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Paleoceanography and Ocean History
How do we reconstruct Earth’s climate history?
Microfossil shell chemistry provides information on ocean temperature & carbon chemistry
Deep Sea Sediments: “Archives of
Earth History” Present
Past
Foraminifera tests ~ calcite (CaCO3)
∆ Ocean Carbon Chemistry ∆ Ocean TemperatureContinental Ice VolumeHydrologic Cycle info
Mass Spectrometers
CO2
Isotopes: 13C/12C 18O/16ONotation: δ13C (‰) δ18O (‰)
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δ18O Time Series Records Evolution of the Cryosphere
Pliocene Pleistocene
Note wavelength and amplitude change
Raymo (1994)
Ice Volume Change
Warm/less ice
Cold/more ice
Glacial-interglacial impact of Rayleigh Fractionation
https://upload.wikimedia.org/wikipedia/commons/6/6f/Glacial_effect_hg.png
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Antarctica Glaciates
Ice-free
12 10 8 6 4°C Zachos et al., 2001
Deep-ocean Benthic Foraminifera Stable Isotopes
PETM Paleocene-Eocene Thermal maximum
Zeebe et al 2008 Paleocene-Eocene Thermal Maximum
(PETM) Event at 55 Ma
This change in fossil chemistry indicates the deep ocean warmed up 6-7C and a lot of carbon entered the ocean quickly
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Dickens et al (1995)
Modern Short-term Exchangeable Carbon Reservoirs
Methane hydrate off the coast of California (modern @ 1000 m depth)
Chapman et al 2004 (EOS)
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55 Ma Methane Hydrate Release, Oxidation, and Mixing Model
3.Mixing sfc-deep
102-103 yr
3. CO2 mixes into deep ocean (~103 y)
Atmosphere
2. Methane converts to CO2 (atmosphere and mixed layer)
2. CH4 CO2 10-100 yr
1. Gradual warming triggers methane hydrate dissociation (~ 102 Gt in 102 yr, ~ 103 Gt in 103 - 104 yr)
1. CH4
200 + 1000 Localized
40000
1200
700 Gt
New proxies from the lab: Mg/Ca gives us a pure temperature reconstruction tool
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500,000 yr Pacific SST record 500,000 year record of SST
Linking oxygen isotopes and Mg/Ca allowed us to reconstruct the tropical hydrological cycle in the past: Tropical rainfall can change dramatically in
<50 years Dr. Matthew Schmidt
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�
How Small Can we go? New �Tools for Tomorrow’s questions
On-going collaborations between Howie Spero, Spider Vetter (UC Davis), Claudia Mora (LANL) & Steve Eggins (ANU)
Excimer Laser ICP-MS SIMS/nanoSIMS/IRMS
Gem quality Iceland spar
Deep UV laser (<200 nm) and low pulse energy (~0.1-0.2 GW/cm2) Each laser pulse shaves ~100 nm layer from test surface
10 laser pulses 100 laser pulses
The Tools LA-ICPMS depth profiling
Eggins et al (2004) Pulleniatina obliquiloculata
Neogloboquadrina dutertrei
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Spero, (1988)
POM POM
Outer sfc
Inner
Outer Sfc
Inner
Spine
10 µm
5 µm 100 µm
1 µm
~1 day old shell wall
Post-gametogenic shell
Sphere Development thru ontogeny
~2 day old shell wall
Thin organic layer
0
4
8
12
0
1
2
3
4
0 5 10 15 20 25
Specimen 103
Mg/
Ca (m
Mol
/Mol
)
Ba/Ca (µMol/M
ol)
Depth (µm)
Mg/Ca
Ba/Ca
Outersurface
Innersurface
POM
Spero et al., (2015)
LA-ICPMS profile of O. universa grown on 12h:12h L:D cycle @ 20C in seawater
One days growth adds ~4-5 µm to the shell wall
NanoSIMS image of Orbulina wall [Mg]
Ba/Ca is constant thru shell
Aleksy Sadekov (unpub image)
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Orbulina universa can be transferred between different culture jars that have normal or
geochemically modified seawater to label calcite
O. universa in culture
Low Mg/Ca bands are added during the day
12h Day Ba - Spike
0
4
8
12
0
1
2
3
4
0 5 10 15 20
Specimen 452a
Mg/
Ca (m
Mol
/Mol
) Ba/Ca (µMol/M
ol)
Depth (µm)
Mg/Ca
Ba/Ca
Outersurface
Innersurface
POMPredicted ambient Ba/Ca
test
Spero et al., (2015) Hönisch et al
(2011)
Left images - Laser Confocal Microscopy of O. universa with vital stains for mitochondria (red) and symbiont
chlorophyll (blue). Right Images are light microscopy/SEM Mitochondria
(red)
Symbiont chlorophyll
(blue)
Symbionts
Images by Russell, Fehrenbacher, Branson
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SIMS (secondary ion mass spectrometry)
U. Wisconsin SIMS – Cameca 1280
Spider Vetter, Claudia Mora and Reinhard
Kozdon analyzing cultured foraminifera
Resolving 12/24 hr intrashell calcite bands in an O. universa shell
SIMS spots across O. universa chamber; 2x3 µm for δ18O
~20 µm thick
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(Vetter et al., 2013)
Full δ18Oc shift is recorded across 2-3 µm
of calcite!
Multiple spots are needed to obtain statistically relevant averages
Predicted δ18O = -3.3‰ Spot avg. δ18O = -3.2‰
• 2σ individual spot s.d. (all runs) ranges between ±0.3-1.1‰ • 2σ experiment s.e. = ±0.4‰ (n=9)
SIMS spot = 8 µm
Std. Error on measured spots (2σ) = ±0.3‰ (n=16)
Vetter et al (2014)
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Charlotte LeKieffre and Anders Meibom Univ. Lausanne, Switzerland
Charlotte LeKieffre on NanoSIMS 50L
Exploring carbon and nitrogen flow through a symbiont system using 13C and 15N- labeled DIC and DIN and
TEM/NanoSIMS
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Diurnal rhythm in a symbiotic planktonic foraminifera
Day Night
Symbionts migrate into vacuoles in foraminifera at night and move on to spines during the day
0.5 µm
Chloroplasts Nucleus Pyrenoid
Starch sheath around pyrenoid – fixed Carbon
Combining TEM and NanoSIMS to explore symbiont to host carbon update and
translocation Dinoflagellate
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Charlotte LeKieffre, Anders Meiobom (Univ. Lausanne; unpub data)
TEM NanoSIMS 13C/12C
Charlotte LeKieffre, Anders Meiobom (Univ. Lausanne; unpub data)
TEM
NanoSIMS 13C/12C
Combined – showing 13C in starch sheath
around pyrenoids
NanoSIMS + TEM Combined
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lipids
Charlotte LeKieffre, Anders Meiobom (Univ. Lausanne; unpub data)
At night…..symbionts move fixed carbon to the foraminifera. 13C labeled carbon shows up in lipids and cytoplasm
TEM NanoSIMS Combined
Insights into symbiont carbon translocation and bouyancy
Le Kieffre, Spero, Russell, Fehrenbacher, Geslin and Meibom (in prep)
Starch to lipid appears to be the first step in C translocation. Possible bouyancy mechanism?
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Double labeling symbionts with 13C-DIC and 15N-NO3 – 6 hrs in label
δ13C
δ15N
symbiont
N P
S
N = nucleus, P = pyrenoid/chloroplast, S = starch, F = foram cytoplasm
F
Double labeling symbionts with 13C-DIC and 15N-NH4 – 6 hrs in label
δ13C
δ15N
N = nucleus, P = pyrenoid/chloroplast, S = starch, F = foram cytoplasm
N
P
S
F
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Double labeled food; 13C- and 15N-labeled Artemia – 8 hrs after feed
δ13C
δ15N
Food vacuoles
….hmmm… What can I do with this technique? What if you could localize where N-fixation was occurring in forest soil ecosystems?
FLEC = Fluorescently Labeled Embedded Core
Epiflourescence micrographs of a FLEC core showing foraminifera in life position
TEM image of foraminifera
Foram in life position
Sediment surface
If you can see it, you can quantify it with 15N and 13C isotopes - w/µm rez
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The Geochemistry Frontier….. • New instrumentation/applications are ushering in the
next growth phase in stable isotope and elemental geochemistry
• Techniques such as IRMS, LA-ICP-MS, SIMS and NanoSIMS, TEM are mutually compatible and offer a view of spatial variation in materials that has not been previously possible.
• BUT….. SIMS, NanoSIMS, LA-ICP-MS are the wrong tools for >90% of our questions!
• HOWEVER……they are the tools that will likely yield many of the breakthrough discoveries over the next decade. So pick your problems and tools carefully.
Howie’s Crystal Ball for 2020 - Where is isotope biogeochemistry headed?
• Technological advances now permit us to resolve micron/submicron scale variations in sample isotope and elemental composition
• Now….imagine using the full elemental suite in
combination with C,O,H,N,S isotopes On The Same Samples with this level of resolution!
• Wow - The skies the limit……